.\" release 4
.nr LL 5.5i
.ad b
.hy 1
.TH PROJ 1 "2000/03/21 Rel. 4.4" 
.SH NAME
cs2cs \- cartographic coordinate system filter
.SH SYNOPSIS
.B cs2cs
[
.B \-eEfIlrstvwW
[
.I args
] ] [
.B +opts[=arg]
]
.br
      [ \fB+to\fR [\fB+opts\fR[\fB=arg\fR]] ]
file[s]
.SH DESCRIPTION
.I Cs2cs
performs transformation between the source and destination cartographic
coordinate system on a set of input points.  The coordinate system
transformation can include translation between projected and geographic 
coordinates as well as the application of datum shifts.
.PP
The following control parameters can appear in any order:
.TP
.BI \-I
method to specify inverse translation, convert from \fB+to\fR coordinate
system to the primary coordinate system defined.
.TP
.BI \-t "a"
.I A
specifies a character employed as the first character to denote
a control line to be passed through without processing.
This option applicable to ascii input only.
(# is the default value).
.TP
.BI \-e " string"
.I String
is an arbitrary string to be output if an error is detected during
data transformations.
The default value is: *\et*.
Note that if the
.B \-b,
.B \-i
or
.B \-o
options are employed, an error is returned as HUGE_VAL
value for both return values.
.TP
.BI \-E
causes the input coordinates to be copied to the output line
prior to printing the converted values.
.TP
.BI \-l "[p|P|=|e|u|d]" id
List projection identifiers with
.B \-l,
.B \-lp
or
.B \-lP (expanded)
that can be selected with
.B +proj.
.BI \-l= id
gives expanded description of projection
.I id.
List ellipsoid identifiers with
.B \-le,
that can be selected with
.B +ellps,
.B \-lu
list of cartesian to meter conversion factors
that can be selected with
.B +units
or
.B \-ld
list of datums that can be selected with 
.B +datum.
.TP
.BI \-r
This options reverses the order of the
expected input from longitude-latitude or x-y to latitude-longitude or y-x.
.TP
.BI \-s
This options reverses the order of the
output from x-y or longitude-latitude to y-x or latitude-longitude.
.TP
.BI \-m " mult"
The cartesian data may be scaled by the
.I mult
parameter.
When processing data in a forward projection mode the
cartesian output values are multiplied by
.I mult
otherwise the input cartesian values are divided by
.I mult
before inverse projection.
If the first two characters of
.I mult
are 1/ or 1: then the reciprocal value of
.I mult
is employed.
.TP
.BI \-f " format"
.I Format
is a
.I printf
format string to control the form of the output values.
For inverse projections, the output will be in degrees when this option
is employed.
If a format is specified for inverse projection the
output data will be in decimal degrees.
The default format is "%.2f" for forward projection and DMS
for inverse.
.TP
.BI \-[w|W] n
.I N
is the number of significant fractional digits to employ for
seconds output (when the option is not specified,
.B \-w3
is assumed).
When
.B \-W
is employed the fields will be constant width and with leading zeroes.
.TP
.B \-v
causes a listing of cartographic control parameters tested for and
used by the program to be printed prior to input data.
Should not be used with the
.B \-T
option.
.PP
The
.B +args
run-line arguments are associated with cartographic parameters
and usage varies with projection and for a complete description see
.I "Cartographic Projection Procedures for the UNIX Environment\(emA User's Manual" )
and supplementary documentation for Release 4.
.PP
The \fIcs2cs\fR program requires two coordinate system definitions.  The
first (or primary is defined based on all projection parameters not
appearing after the \fB+to\fR argument.  All projection parameters 
appearing after the \fB+to\fR argument are considered the definition
of the second coordinate system.  If there is no second coordinate system
defined, a geographic coordinate system based on the datum and ellipsoid of
the source coordinate system is assumed.  Note that the source and destination
coordinate system can both be projections, both be geographic, or one of
each and may have the same or different datums.  
.PP
Additional projection control parameters may be contained in two
auxilliary control files:
the first is optionally referenced with the
.BI +init= file:id
and the second is always processed after the name
of the projection has been established from either the run-line
or the contents of
.B +init
file.
The environment parameter
.B PROJ_LIB
establishes the default directory for a file reference without
an absolute path.  This is also used for supporting files like
datum shift files.
.PP
One or more
.I files
(processed in left to right order)
specify the source of data to be transformed.
A \- will specify the location of processing standard input.
If no files are specified, the input is assumed to be from
.I stdin.
For input data the two data values must be in the
first two white space separated fields and
when both input and output are ASCII all trailing portions
of the input line are appended to the output line.
.PP
Input geographic data
(longitude and latitude) must be in DMS format and input
cartesian data must be in units consistent with the ellipsoid
major axis or sphere radius units.
Output geographic coordinates will be in DMS
(if the
.B \-w
switch is not employed) and precise to 0.001"
with trailing, zero-valued minute-second fields deleted.
.SH EXAMPLE
The following script
.RS 5
 \f(CWcs2cs +proj=latlong +datum=NAD83 
       +to +proj=utm +zone=10 +datum=NAD27 -r <<EOF
 45d15'33.1"	111.5W
 45d15.551666667N	-111d30
 +45.25919444444	111d30'000w
 EOF\fR
.RE
will transform the input NAD83 geographic coordinates into NAD27 coordinates
in the UTM projection with zone 10 selected.
The geographic values of this example are equivalent and meant
as examples of various forms of DMS input.
The x\-y output data will appear as three lines of:
.RS 5
 \f(CW1402285.99      5076292.42 0.000
.RE
.SH SEE ALSO
.B proj(1U),
.br
.I "Cartographic Projection Procedures for the UNIX Environment\(emA User's Manual,"
(Evenden, 1990, Open-file report 90\-284).
.br
.I "Map Projections Used by the U. S. Geological Survey"
(Snyder, 1984,
USGS Bulletin 1532).
.br
.I "Map Projections\(emA Working Manual"
(Synder, 1988, USGS Prof. Paper 1395).
.br
.I "An Album of Map Projections"
(Snyder & Voxland, 1989, USGS Prof. Paper 1453).
.SH HOME PAGE
http://www.remotesensing.org/proj
